As I understand it, it is more complicated than "built-in vs 3rd-party". There are:
- core features
- elisp which is part of the default emacs distribution
- elisp which is part of the default emacs package repository (elpa)
- elisp which is part of alternative emacs distributions
- elisp packages bundled together into user-friendly initial configurations (prelude, ergoemacs...)
- elisp which is maintained and available on melpa, github...
- ad-hoc elisp snippets (available on emacswiki or stackoverflow for example).
Add to that the existence of different flavors of emacs, each with its own set of specific features... For example, if a user asks for tabs in the emacs UI, aquamacs users will tell him that it is built in, while vanilla emacs users will need a 3rd party package. Not even mentioning the different emacs versions ("does there exist a package manager?" or "how to change the color theme?" in pre-24 for example).
But it isn't a problem that is exclusive to emacs either. A C++ question on SO can get one answer using only built-in features, another with the standard library, and another with ad-hoc code. Votes will just select the most convenient one.
This would work here as well: let each answer advertise its favorite way of doing things, and the asker will pick the one he likes most (or even try several).